Compressor

ABSTRACT

A compressor includes an impeller including blades extending along a shroud. Each of the blades includes a leading edge, a trailing edge, and a tip edge connecting the leading edge and the trailing edge and opposing the shroud. The tip edge has a central curve extending along a center of a thickness of the tip edge from the leading edge to the trailing edge. The central curve has a tangential line touching a contact in the central curve. The tangential line has a tip edge inclination angle made by the rotation axis and the tangential line viewed in a reference direction which passes the contact and which is perpendicular to the rotation axis. The tip edge inclination angle increases as the contact approaches a first maximum inclination point in the central curve. The first maximum inclination point is separated from both the leading edge and the trailing edge.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2016-083764, filed Apr. 19, 2016, entitled “Compressor.” The contents of this application are incorporated herein by reference in their entirety.

BACKGROUND 1. Field

The present disclosure relates to a compressor.

2. Description of the Related Art

Hitherto, in a case in which a fixed diffuser is disposed downstream of a compressor that compresses an intake flowing in an intake passage of an internal-combustion engine, the air compressed in the compressor impeller generates a nozzle wake (a pressure fluctuation) when passing through the fixed diffuser. With the above, the compressor impeller positioned upstream receives exciting force caused by the nozzle wake and a phenomenon in which the blades of the compressor impeller vibrate occurs.

Responding to the above, from the viewpoint of securing blade strength against the blade vibration, one may conceive of forming the blade of the compressor impeller with a thick cross-sectional blade shape. However, there is a trade-off relationship between the blade strength and the aerodynamic performance of the compressor impeller. Loss is caused by the thickness of the blade creating a limit to the above adjustment.

Meanwhile, cutting off (cutback) of the trailing edge of the blade of the compressor impeller has been performed; however, in such a case, the compressed air flowing out from the compressor impeller flows into the fixed diffuser in an unstable state. Accordingly, as a result of decrease in the static pressure efficiency at the compressor impeller outlet, a problem of decrease in supercharging efficiency occurs.

Furthermore, with the aim of improving the supercharging efficiency, a compressor in which the trailing edge of the blade is formed with a peripheral surface having a substantially semi-elliptic cylindrical shape has been disclosed (see Japanese Unexamined Patent Application Publication No. 2009-41373, for example). It is described that the separation of the fluid can be suppressed at the trailing edge of the blade.

SUMMARY

According to one aspect of the present invention, a compressor that compresses a fluid, includes: a housing in which a shroud is formed; an impeller provided inside the housing, the impeller being provided so as to be rotatable about a rotating shaft; and a diffuser provided around the impeller, the diffuser decelerating the intake discharged from a trailing edge of the impeller in a centrifugal direction. In the compressor, the impeller includes a conical wheel, and a plurality of blades extending on an outer peripheral surface of the wheel and along the shroud from a leading edge that is an inlet of the intake towards the trailing edge that is an outlet of the intake, in which in a case in which a central curve of a thickness of a tip edge of each blade, the tip edge opposing the shroud, is projected on a virtual plane including an axis of the rotating shaft, an angle formed, at an intersection point between the central curve projected on the virtual plane and the axis, between a tangential line of the central curve that has been projected and the axis is defined, as a definition, as a tip edge angle, and under the definition, an angular distribution of the tip edge protrudes upwards from the leading edge to the trailing edge, and in which in a cross section of the trailing edge of the blade has an elliptical arc shape or an arc shape.

According to another aspect of the present invention, a compressor includes a housing, an impeller, and a diffuser. The housing includes an air intake and a compressor impeller chamber opposite to the air intake along a rotation axis. The compressor impeller chamber includes a shroud therein. The impeller is provided opposite to the shroud in the compressor impeller chamber to be rotatable around the rotation axis. The impeller includes a wheel and blades. The wheel has a substantially conical shape around the rotation axis and is provided such that the substantially conical shape tapering toward the air intake. The blades are provided on an outer peripheral surface of the substantially conical shape of the wheel and extend along the shroud. Each of the blades includes a leading edge, a trailing edge, and a tip edge. The leading edge is closest to the air intake. A cross section of the trailing edge taken along a reference plane has a substantially elliptical arc shape or a substantially arc shape. The reference plane contacts the trailing edge to be parallel to the outer peripheral surface. The tip edge connects the leading edge and the trailing edge and opposes the shroud. The tip edge has a central curve extending along a center of a thickness of the tip edge from the leading edge to the trailing edge. The central curve has a tangential line touching a contact in the central curve. The tangential line has a tip edge inclination angle made by the rotation axis and the tangential line viewed in a reference direction which passes the contact and which is perpendicular to the rotation axis. The tip edge inclination angle increases as the contact approaches a first maximum inclination point in the central curve. The first maximum inclination point is separated from both the leading edge and the trailing edge. The diffuser is provided around the impeller to decelerate the fluid discharged from the trailing edge of the impeller in a centrifugal direction with respect to the rotation axis.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings.

FIG. 1 is a cross-sectional view illustrating a configuration of a supercharger using a compressor according to an exemplary embodiment of the present disclosure.

FIG. 2 is a perspective view of a compressor impeller.

FIG. 3 is a front view of the compressor impeller.

FIG. 4 is a side view of the compressor impeller.

FIG. 5A is a perspective view of a base of a trailing edge portion of a main blade.

FIG. 5B is a diagram schematically illustrating a procedure for forming a protruded portion.

FIG. 6A is a diagram illustrating angular distributions of the main blade of the present exemplary embodiment that has an overturned shape.

FIG. 6B is a diagram illustrating angular distributions of a conventional main blade that does not have an overturned shape.

FIG. 7A is a diagram illustrating a shape of a tip edge of the conventional main blade that does not have an overturned shape.

FIG. 7B is a diagram illustrating a shape of a tip edge of the main blade according to the present exemplary embodiment that does have an overturned shape.

DESCRIPTION OF THE EMBODIMENTS

The embodiment(s) will now be described with reference to the accompanying drawings, wherein like reference numerals designate corresponding or identical elements throughout the various drawings.

Hereinafter, an exemplary embodiment of the present disclosure will be described with reference to the drawings.

FIG. 1 is a cross-sectional view illustrating a configuration of a supercharger 1 using a compressor according to the present exemplary embodiment.

The supercharger 1 includes a turbine 3 mounted on one end of the bearing housing 2, and a compressor 6 mounted on the other end of the bearing housing 2. The bearing housing 2 includes a rod-shaped rotating shaft 21 extending between the turbine 3 and compressor 6, and a bearing 22 that rotatably supports the rotating shaft 21.

The turbine 3 includes a turbine housing 4 constituting a portion of an exhaust passage of an internal-combustion engine (not shown), and a turbine impeller 5 provided inside the turbine housing 4.

A tubular exhaust intake 41 connected to exhaust pipes of the internal-combustion engine, an annular scroll passage 42 through which the exhaust taken in from the exhaust intake 41 flows, a tubular turbine impeller chamber 43 formed so as to be surrounded by the scroll passage 42, and an annular exhaust flow path 45 connecting the scroll passage 42 and a base end side of the turbine impeller chamber 43 to each other are provided in the turbine housing 4.

The turbine impeller 5 is rotatably provided inside the turbine impeller chamber 43 while connected to one end side of the rotating shaft 21. A plurality of blade-shaped nozzle vanes 46 are provided in the exhaust flow path 45 at equal intervals in a circumferential direction of the rotating shaft 21 and at a predetermined angle with respect to the circumferential direction, so as to surround the base end side of the turbine impeller chamber 43.

The compressor 6 includes a compressor housing 7 constituting a portion of an intake passage of the internal-combustion engine, and a compressor impeller 8 and a diffuser 9 provided inside the compressor housing 7.

A tabular compressor impeller chamber 72, an air intake 71 that is connected to an intake pipe (not shown) of the internal-combustion engine and that is formed on a distal end side thereof and a shroud 75 formed on a base end side thereof, an annular scroll passage 73 formed so as to surround the compressor impeller chamber 72, and an annular intake flow path 74 connecting the base end side of the compressor impeller chamber 72 and the scroll passage 73 to each other are formed in the compressor housing 7.

The compressor impeller 8 is rotatably provided inside the shroud 75 while connected to the other end side of the rotating shaft 21. The diffuser 9 is disk-shaped and is provided in the intake flow path 74. The diffuser 9 compresses the intake by decelerating the intake that is discharged in a centrifugal direction of the rotating shaft 21 from a base end side of the shroud 75 towards the scroll passage 73. Note that detailed configurations of the compressor impeller 8 and the diffuser 9 will be described later with reference to FIGS. 2 to 7.

According to the following procedure the supercharger 1 configured in the above manner supercharges the intake by using the energy of the exhaust of the internal-combustion engine.

The exhaust of the internal-combustion engine is first introduced into the scroll passage 42 through the exhaust intake 41. The exhaust made to swirl by passing through the scroll passage 42 flows into the base end side of the turbine impeller chamber 43 at a predetermined angel with the nozzle vanes 46, rotates the turbine impeller 5, and is discharged from the discharge portion 47 provided on the distal end side of the turbine impeller chamber 43. The rotation of the turbine impeller 5 is transmitted to the compressor impeller 8 through the rotating shaft 21 and the compressor impeller 8 rotates inside the compressor impeller chamber 72. The intake that has been introduced into the compressor impeller chamber 72 through the air intake 71 is discharged in the centrifugal direction towards the scroll passage 73 from the base end side of the compressor impeller 8 with the rotation of the compressor impeller 8. The intake discharged from the compressor impeller 8 is decelerated while being expanded by the diffuser 9; accordingly, the intake is compressed. The compressed intake flows through the scroll passage 73 and is introduced into intake ports (not shown) of the internal-combustion engine.

FIG. 2 is a perspective view of the compressor impeller 8, FIG. 3 is a plan view of the compressor impeller 8, and FIG. 4 is a side view of the compressor impeller 8.

The compressor impeller 8 includes a conical wheel 81, a plurality of main blades 84 that are plate-shaped blades, and a plurality of splitters 86. The main blades 84 and the splitters 86 are provided on an outer peripheral surface of the wheel 81.

The wheel 81 includes a hub surface 82 that is an outer peripheral surface that extends in a smooth manner to the outside in the centrifugal direction from a distal end side 81 a towards a base end side 81 b of an axis C of the rotating shaft, and a shaft mounting hole 83 that penetrates through the center of the wheel 81 from the base end side 81 b towards the distal end side 81 a. The rotating shaft connected to the turbine impeller is connected to the wheel 81 by a cap (not shown) screwed thereon while inserted in the shaft mounting hole 83. With the above, the compressor impeller 8 and the turbine impeller are integrally connected to each other through the rotating shaft.

The main blades 84 are provided plurally on the hub surface 82 of the wheel 81 at equal intervals in the circumferential direction. Each main blade 84 has a tabular shape that extends on the hub surface 82 in accordance with a predetermined angular distribution (see FIG. 6 described later) from a leading edge portion 841 on the distal end side 81 a, which is an inlet of the intake, towards a trailing edge portion 842 on the base end side 81 b, which is the outlet of the intake. A tip edge 843 of each main blade 84 is formed along a surface shape of the shroud 75 (see FIG. 1) opposing the tip edge 843 when the compressor impeller 8 is received in the compressor impeller chamber.

Each splitter 86 is provided on the hub surface 82 between two adjacent main blades 84 and 84. Each splitter 86 has a tabular shape that extends on the hub surface 82 in accordance with a predetermined angular distribution (see FIG. 6 described later) from a leading edge portion 861 on the distal end side 81 a towards a trailing edge portion 862 on the base end side 81 b. Similar to the tip edge 843 of each main blade 84, the tip edge 863 of each splitter 86 is formed along the surface shape of the shroud 75 (see FIG. 1). The length of each splitter 86 from the leading edge portion 861 to the trailing edge portion 862 is shorter than the length of each main blade 84 from the leading edge portion 841 to the trailing edge portion 842. The leading edge portion 861 of each splitter 86 is provided so as to be positioned on the base end side 81 b with respect to the leading edge portion 841 of the corresponding main blade 84. Furthermore, the trailing edge portion 862 of each splitter 86 is provided so as to be flush with the trailing edge portion 842 of the corresponding main blade 84.

Referring next to FIG. 5A, a configuration of the trailing edge portion 842 of each main blade 84 will be described.

FIG. 5A is a perspective view of a base of the trailing edge portion 842 of each main blade 84.

A thickness of each main blade 84 in the circumferential direction gradually decreases from the hub surface 82 side of the wheel 81 towards the tip edge 843. Furthermore, a section of the trailing edge portion 842 taken along a surface parallel to the hub surface 82 has an elliptical arc shape. With the above, the two surfaces of each main blade 84 are connected by a smooth continuous surface.

Furthermore, in the base of each main blade 84, a corner rounded portion 84 b that smoothly connects two lateral surfaces 84 a of the main blade 84 and the hub surface 82 of the wheel 81 to each other are formed along the perimeter from the leading edge portion 841 to the trailing edge portion 842. As illustrated in FIG. 5A, a section of the corner rounded portion 84 b taken along a surface perpendicular to the main blade 84 has an arc shape. As described above, by forming the corner rounded portion 84 b having an arcuate section in the base of each main blade 84 and, further, by forming each trailing edge portion 842 such that the cross section thereof has an elliptical arc shape, each trailing edge portion 842, the two lateral surfaces 84 a of the corresponding main blades 84, and the hub surface 82 can be connected by a smooth continuous surface.

Furthermore, an outside diameter from a central axis of the compressor wheel to an outer peripheral end surface 81 a of the wheel 81 is slightly larger than an outside diameter from the same central axis to the trailing edge portion 842 of each main blade 84. With the above, an outermost peripheral surface of the compressor wheel is constituted by the outer peripheral end surface 81 a of the wheel 81. Furthermore, in an outer peripheral end portion 81 b of the wheel 81, that is, in connections between the outer peripheral end portions 81 b and the trailing edge portions 842, protruded portions 81 c each having a slightly bulged thickness are formed.

FIG. 5B is a diagram schematically illustrating a procedure for forming the compressor wheel, illustrated in FIG. 5A, including the trailing edge portions 842 each having the elliptical arc shape described above, the corner rounded portions 84 b each having an arcuate section, and the protruded portions 81 c.

As illustrated in FIG. 5B, a wheel in which an outside diameter of the outer peripheral end portion 81 b of the wheel 81 is larger than an outside diameter L defined by the compressor impeller chamber is prepared first. Subsequently, the corner rounded portions 84 b each having an arcuate section are formed in the perimeters of the bases of the main blades 84, and each trailing edge portion 842 is formed such that the cross section thereof has an elliptical arc shape. With the above, as illustrated in FIG. 5B, each trailing edge portion 842, the two lateral surfaces 84 a of the corresponding main blades 84, and the hub surface 82 are connected by a smooth continuous surface without any sharp angles. Subsequently, finishing that scrapes off the outer peripheral end portion 81 b of the wheel 81 so that the outside diameter thereof is the outside diameter L is performed. Accordingly, the compressor wheel including the trailing edge portions 842 and the corner rounded portions 84 b illustrated in FIG. 5A are formed. Note that although illustration and detailed description are omitted, the trailing edge portion 862 of each splitter 86 also has a shape that is substantially similar to that in FIG. 5A.

FIG. 6A is a diagram illustrating angular distributions of the main blade (thin solid line) and the splitter (thick broken line) of the present exemplary embodiment. FIG. 6B is a diagram illustrating angular distributions of a conventional main blade (thin solid line) and a conventional splitter (thick broken line). In each of FIGS. 6A and 6B, angular distributions of the main blade and the splitter on the hub surface side are illustrated on the upper portion side, and angular distributions of the tip edges of the main blade and the splitter are illustrated on the lower portion side. Note that hereinafter, the main blade and the splitter may both be also referred to as, merely, a “blade”. In FIGS. 6A and 6B, the axis of abscissas indicates the distance from the leading edge portion that is the inlet of the intake to a target position, and the axis of ordinates indicates the angle [°] of the blade at the target position. Note that the distance in the axis of abscissas indicates a non-dimensional distance when the distance from the leading edge portion of the main blade to the trailing edge portion, which is the outlet of the intake, is assumed to be 100. As described above, the splitter is shorter than the main blade, and the leading edge portion of splitter is provided on the trailing edge portion side with respect to the leading edge portion of the main blade. Accordingly, as illustrated in FIGS. 6A and 6B, the origin of the thick broken line depicting the angular distribution of the splitter is positioned at a point in the graph that is larger in angle and distance with respect to the position of the origin of the thin solid line depicting the angular distribution of the main blade.

The definition of an angle β of the blade will be described with reference to FIG. 4 that is a side view of the compressor impeller. FIG. 4 illustrates an example of the angle β of the tip edge 843 of the main blade 84 formed under the definition according to the present exemplary embodiment.

In the present exemplary embodiment, the angle β of the above blades is defined by the axis C of the rotating shaft and a virtual plane including the axis C. More specifically, for example, the angle β of the tip edge 843 of each main blade 84 (a tip edge inclination angle β) is defined as, in a case in which a central curve of the thickness of the tip edge 843 is projected on a virtual plane including the axis C, an angle that is formed between a tangential line L2 of a central curve L1 and the axis C at an intersection point P between the central curve L1 projected on the virtual plane and the axis C. Furthermore, in the present exemplary embodiment, the clockwise direction is the positive direction. In other words, the angle β exemplified in FIG. 4 is negative. Furthermore, although illustration is omitted, the angle of the tip edge 863 of each splitter 86, the angles of the main blades 84 and the splitters 86 on the hub surface side are defined in a similar manner using the axis C.

As illustrated in FIGS. 6A and 6B, each thick broken line and the corresponding thin solid line substantially overlap each other. This indicates that the angular distribution of each splitter and the angular distribution of the corresponding main blade are substantially the same.

As illustrated in the upper portions of FIGS. 6A and 6B, the angular distributions of the blades on the hub surface side are that same in the case of the present exemplary embodiment and in the case of the conventional ones, and the angular distributions protrude upwards from the leading edge portion to the trailing edge portion. More specifically, as illustrated in the upper portion of FIG. 6A, the angle of the blade on the hub surface side (a hub surface side angle) is gradually increased from the leading edge portion to a maximum position Pm (a second maximum inclination point Pm) set between the leading edge portion and the trailing edge portion and, further, is gradually decreased from the maximum position Pm to the trailing edge portion.

On the other hand, the angular distributions of the tip edges of the blades are different in the case of the present exemplary embodiment and in the case of the conventional ones. More specifically, as illustrated in the lower portion of FIG. 6B, the angular distribution of the tip edge of the conventional blade slowly increases from the leading edge portion towards the trailing edge portion. Conversely, the angular distribution of the tip edge of the blade of the present exemplary embodiment protrude upwards from the leading edge portion to the trailing edge portion. In other words, in the present exemplary embodiment, the angle of the tip edge of the blade is gradually increased from the leading edge portion to a maximum position Qm (a first maximum inclination point Qm) set between the leading edge portion and the trailing edge portion and, further, is gradually decreased from the maximum position Qm to the trailing edge portion. In other words, the tip edges of the main blade and the splitter are formed across the leading edge portion to the trailing edge portion in a so-called overturned shape that is, after being bent, bent back to the opposite side.

Furthermore, as indicated in the upper and lower portions in FIG. 6A, the angle of the tip edge at the leading edge portion of the main blade is smaller than the angle of the leading edge portion of the main blade on the hub surface side, and the angle of the tip edge at the leading edge portion of the splitter is smaller than the angle of the leading edge portion of the splitter on the hub surface side. The angle of the tip edge of the main blade at the trailing edge portion is substantially the same as the angle of the trailing edge portion of the main blade on the hub surface side and the angle of the tip edge of the splitter at the trailing edge portion is substantially the same as the angle of the trailing edge portion of the splitter on the hub surface side. Furthermore, the positions Qm where the angles of the tip edges of the main blade and the splitter become the largest are nearer to the trailing edge portions than the positions Pm where the angles of the main blade and the splitter on the hub surface side become the largest.

FIG. 7A is a diagram illustrating a shape of the tip edge of the conventional blade that does not have an overturned shape. FIG. 7B is a diagram schematically illustrating the shape of the tip edge of the blade 84 (or 86) of the present exemplary embodiment that has the overturned shape. In the above diagrams, the arrows depict the flow of the fluid.

As illustrated in FIG. 7A, in the tip edge of the conventional blade that does not have an overturned shape, the fluid unable to follow the blade after passing the peak P1 of the bend portion becomes separated. In other words, even if the cross section of the trailing edge portion of the blade were to have an elliptical arc shape, such as the shape illustrated in FIG. 5A, it is considered that suppression of separation is difficult.

Conversely, in the tip edge 843 (or 863) of the blade 84 (or 86) of the present exemplary embodiment that has the overturned shape, since the tip edge 843 (or 863) has a shape that is, after being bent, bent back to the opposite side, the intake follows the blade 84 (or 86) on the trailing edge portion 842 (or 862) side as well. Accordingly, in the blade 84 (or 86) of the present exemplary embodiment, since the shape of the tip edge 843 (or 863) is made to have the overturned shape in addition to having the cross section of the trailing edge portion 842 (or 862) of the blade 84 (or 86) have an elliptical arc shape, separation of the fluid can be suppressed.

The compressor impeller 8 configured in the above manner rotates in the clockwise direction in FIG. 2 when the turbine impeller connected to the compressor impeller 8 with the rotating shaft is rotated by the exhaust blown thereto. When the compressor impeller 8 is rotated while provided inside the compressor impeller chamber, the intake flowing in from the distal end side 81 a flows in a direction parallel to the axis C to the leading edge portion 841 of each main blade 84 and the leading edge portion 861 of each splitter 86, flows between the main blades 84 and the splitters 86, and is discharged towards the outside in the centrifugal direction from each of the trailing edge portions 842 and 862.

Referring back to FIG. 1, the diffuser 9 is disk-shaped having an outside diameter that is larger than an outside diameter of the compressor impeller 8. The diffuser 9 surrounding the base end side of the compressor impeller 8 is fixed to the annular intake flow path 74 of the compressor housing. The diffuser 9 includes a discoidal disk, and a cascade of blades provided on the front surface of the disk. The cascade of blades is composed of a plurality of linear blades provided on the front surface of the disk so as to be erect at equal intervals in the circumferential direction about the axis C of the rotating shaft 21.

The function of the diffuser 9 configured in the above manner will be described. When the compressor impeller 8 rotates about the rotating shaft 21, the intake is taken in towards the compressor impeller 8 side in a direction parallel to the axis C and, then, is discharged towards the outside in the centrifugal direction along the front surface of the diffuser 9 through the trailing edge portions 842 and 862. The intake discharged from the compressor impeller 8 expands to the outside in the centrifugal direction while being decelerated by the cascade of blades provided in the diffuser 9 and, as a result, the pressure of the intake is increased.

Effects described below can be obtained with the present exemplary embodiment.

In the present exemplary embodiment, in the blades 84 and 86, the angular distribution of each of the tip edges 843 and 863 is configured to protrude upwards from the corresponding one of the leading edge portions 841 and 861 to the corresponding one of the trailing edge portions 842 and 862. In other words, the tip edges 843 and 863 of the main blades 84 and the splitters 86 are formed across the leading edge portions 841 and 861 to the trailing edge portions 842 and 862 in a so-called overturned shape that is, after being bent, bent back to the opposite side. With the above, the fluid can be made to follow the blades 84 and 86 across the leading edge portions 841 and 861 and the trailing edge portions 842 and 862 of the blades 84 and 86 without being separated.

Furthermore, in the present exemplary embodiment, the cross sections of the trailing edge portions 842 and 862 of the blades 84 and 86 have elliptical arc shapes. With the above, the fluid that has, owing to the employment of the overturned shape described above, followed the blades 84 and 86 to the trailing edge portions 842 and 862 without being separated can be made to follow the blades 84 and 86 in the trailing edge portions 842 and 862 as well without being separated. At the same time, the influence of the nozzle wake created downstream of the diffuser 9 can be reduced and the vibration of the blades 84 and 86 can be suppressed.

Accordingly, in the present exemplary embodiment, the vibrations of the blades 84 and 86 of the compressor impeller 8 and the separation of the fluid can be suppressed and the supercharging efficiency can be improved.

Furthermore, in the present exemplary embodiment, the corner rounded portion that has an arcuate cross section and that smoothly connects the two lateral surfaces of the blades 84 and 86 and the hub surface 82 of the wheel 81 to each other is formed in each of the bases of the blades 84 and 86 on the trailing edge portion 842 and 862 side. With the above, the trailing edge portions 842 and 862 of the blades 84 and 86 formed such that the cross sections have an elliptical arc shape, the two lateral surfaces of the blades 84 and 86, and the hub surface 82 of the wheel 81 can be connected with a smooth continuous surface without any sharp angles. Accordingly, the effects described above can be obtained reliably.

Furthermore, in the present exemplary embodiment, the thicknesses of the blades 84 and 86 are configured to gradually decrease from the wheel 81 side towards the tip edges 843 and 863. With the above, the effects described above can be obtained while the strength of the blades 84 and 86 is secured.

Furthermore, in the present exemplary embodiment, the angular distribution of each of the blades 84 and 86 on the hub surface side is also configured to protrude upwards from the corresponding leading edge portion to the corresponding trailing edge portion, the angles of the tip edges 843 and 863 at the leading edge portions 841 and 861 are smaller than the angles of the leading edge portions 841 and 861 on the hub surface side, the angles of the tip edges 843 and 863 at the trailing edge portions 842 and 862 are substantially the same as the angles of the trailing edge portions 842 and 862 on the hub surface side, and the positions Qm where the angles of the tip edges 843 and 863 become the largest are nearer to the trailing edge portions 842 and 862 than the positions Pm where the angles on the hub surface side becomes the largest. With the above, the effect of suppressing the separation of the intake can be improved further and, consequently, the supercharging efficiency can be improved further.

Note that the present disclosure is not limited to the exemplary embodiment described above and deformation and modification within the scope of the present disclosure are included in the present disclosure.

In the exemplary embodiment described above, while the trailing edge portion 842 of each main blade 84 and the trailing edge portion 862 of each splitter 86 are formed such that the cross sections taken along surfaces parallel to the hub surface 82 have an elliptical arc shape, the present disclosure is not limited to the above. Even when the trailing edge portion of each blade is formed so as to have an arc-shaped cross section, an effect that is substantially the same as above can be obtained.

In the present exemplary embodiment, description has been given of a case in which the compressor of the present disclosure is used in a supercharger that compresses the intake taken in by an internal-combustion engine; however, the present disclosure is not limited to the above. The compressor of the present disclosure may be used in, other than a supercharger of an internal-combustion engine, turbomachinery that converts an energy of a fluid into a mechanical energy by using an impeller, such as a jet engine, a pump, and the like.

The present disclosure provides a compressor (a compressor described later, for example) that compresses a fluid, the compressor including a housing (a housing described later, for example) in which a shroud (a shroud 75 described later, for example) is formed; an impeller (a compressor impeller described later, for example) provided inside the housing, the impeller being provided so as to be rotatable about a rotating shaft (a rotating shaft described later, for example); and a diffuser (a diffuser described later, for example) provided around the impeller, the diffuser decelerating the intake discharged from a trailing edge of the impeller in a centrifugal direction. In the compressor, the impeller includes a conical wheel (a wheel described later, for example), and a plurality of blades (main blades or splitters described later, for example) extending on an outer peripheral surface of the wheel and along the shroud from a leading edge (a leading edge portion or described later, for example) that is an inlet of the intake towards the trailing edge (a trailing edge portion or described later, for example) that is an outlet of the intake, in which in a case in which a central curve of a thickness of a tip edge (a tip edge or described later, for example) of each blade, the tip edge opposing the shroud, is projected on a virtual plane including an axis (an axis described later, for example) of the rotating shaft, an angle (an angle described later, for example) formed, at an intersection point (an intersection point described later, for example) between the central curve (a central curve described later, for example) projected on the virtual plane and the axis, between a tangential line (a tangential line described later, for example) of the central curve that has been projected and the axis is defined, as a definition, as a tip edge angle, and under the definition, an angular distribution of the tip edge protrudes upwards from the leading edge to the trailing edge, and in which in a cross section of the trailing edge of the blade has an elliptical arc shape or an arc shape.

In the present disclosure, in the blades, the angular distribution of each of the tip edges opposing the shroud is configured to protrude upwards from the corresponding leading edge to the corresponding trailing edge. In other words, the angle of each tip edge is gradually increased from the leading edge towards the position where the angle is largest, and is gradually decreased from the positon where the angle is largest towards the trailing edge. In other words, the tip edge of the blades is formed across the leading edge to the trailing edge in a so-called overturned shape that is, after being bent, bent back to the opposite side. With the above, the intake can be made to follow the blades across the leading edges and the trailing edges of the blades without being separated.

Furthermore, in the present disclosure, the trailing edge of each blade is formed to have an elliptical arc shape or an arc shape. With the above, the intake that has, owing to the employment of the overturned shape described above, followed the blades to the trailing edges without being separated can be made to follow the blades in the trailing edges as well without being separated. At the same time, the influence of the nozzle wake created downstream of the diffuser can be reduced and the vibration of the blades can be suppressed.

Accordingly, in the present disclosure, the vibrations of the blades of the compressor impeller and the separation of the fluid can be suppressed and the supercharging efficiency can be improved.

Desirably, a corner rounded portion (a corner rounded portion described later, for example) that has an arcuate cross section and that smoothly connects a lateral surface (a lateral surface described later, for example) of the blade and a hub surface (a hub surface described later, for example) of the wheel is formed at a base of each blade on a trailing edge side, and a thickness of each blade gradually decreases from a wheel side towards the tip edge.

In the present disclosure, the corner rounded portion that has an arcuate cross section and that smoothly connects the lateral surface of the blade and the hub surface of the wheel is formed at a base of each blade on the trailing edge side. With the above, the trailing edges of the blades formed such that the cross sections have an elliptical arc shape, the two lateral surfaces of the blades, and the hub surface of the wheel can be connected with a smooth continuous surface. Accordingly, the effects described above can be obtained reliably.

Furthermore, in the present disclosure, the thicknesses of the blades are configured to gradually decrease from the wheel side towards the tip edges. With the above, the effects described above can be obtained while the strength of the blades is secured.

In the compressor, in a case in which a central curve of a thickness of each blade on a hub surface side connected to a hub surface is projected on a virtual plane including an axis of the rotating shaft, an angle formed, at an intersection point between the central curve projected on the virtual plane and the axis, between a tangential line of the central curve that has been projected and the axis is defined, as a definition, as a hub surface side angle, and under the definition, an angular distribution on the hub surface side protrudes upwards from the leading edge to the trailing edge, the angle of the tip edge at the leading edge is smaller than the angle of the leading edge on the hub surface side, the angle of the tip edge at the trailing edge is substantially equivalent to the angle of the trailing edge on the hub surface side, and a position (a position Qm described later, for example) where the angle of the tip edge is largest is nearer to the trailing edge than a position (a position Pm described later, for example) where the angle on the hub surface side is largest.

In the present disclosure, the angular distribution of each of the blades on the hub surface side is also configured to protrude upwards from the corresponding leading edge to the corresponding trailing edge, the angles of the tip edges at the leading edges are smaller than the angles of the leading edges on the hub surface side, the angles of the tip edges at the trailing edges are substantially the same as the angles of the trailing edges on the hub surface side, and the positions where the angles of the tip edges become the largest are nearer to the trailing edges than the positions Pm where the angles on the hub surface side becomes the largest. With the above, the effect of suppressing the separation of the fluid can be improved further and, consequently, the supercharging efficiency can be improved further.

Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein. 

What is claimed is:
 1. A compressor that compresses a fluid, the compressor comprising: a housing in which a shroud is formed; an impeller provided inside the housing, the impeller being provided so as to be rotatable about a rotating shaft; and a diffuser provided around the impeller, the diffuser decelerating the fluid discharged from a trailing edge of the impeller in a centrifugal direction, wherein the impeller includes a conical wheel, and a plurality of blades extending on an outer peripheral surface of the wheel and along the shroud from a leading edge that is an inlet of the fluid towards the trailing edge that is an outlet of the fluid, wherein in a case in which a central curve of a thickness of a tip edge of each blade, the tip edge opposing the shroud, is projected on a virtual plane including an axis of the rotating shaft, an angle formed, at an intersection point between the central curve projected on the virtual plane and the axis, between a tangential line of the central curve that has been projected and the axis is defined, as a definition, as a tip edge angle, and under the definition, an angular distribution of the tip edge protrudes upwards from the leading edge to the trailing edge, and wherein a cross section of the trailing edge of the blade has an elliptical arc shape or an arc shape.
 2. The compressor according to claim 1, wherein a corner rounded portion that has an arcuate cross section and that smoothly connects a lateral surface of the blade and a hub surface of the wheel is formed at a base of each blade on a trailing edge side, and wherein a thickness of each blade gradually decreases from a wheel side towards the tip edge.
 3. The compressor according to claim 1, wherein in a case in which a central curve of a thickness of each blade on a hub surface side connected to a hub surface is projected on a virtual plane including an axis of the rotating shaft, an angle formed, at an intersection point between the central curve projected on the virtual plane and the axis, between a tangential line of the central curve that has been projected and the axis is defined, as a definition, as a hub surface side angle, and under the definition, an angular distribution on the hub surface side protrudes upwards from the leading edge to the trailing edge, wherein the angle of the tip edge at the leading edge is smaller than the angle of the leading edge on the hub surface side, wherein the angle of the tip edge at the trailing edge is substantially equivalent to the angle of the trailing edge on the hub surface side, and wherein a position where the angle of the tip edge is largest is nearer to the trailing edge than a position where the angle on the hub surface side is largest.
 4. A compressor comprising: a housing including an air intake and a compressor impeller chamber opposite to the air intake along a rotation axis, the compressor impeller chamber including a shroud therein; an impeller provided opposite to the shroud in the compressor impeller chamber to be rotatable around the rotation axis, the impeller comprising: a wheel having a substantially conical shape around the rotation axis and provided such that the substantially conical shape tapering toward the air intake; and blades provided on an outer peripheral surface of the substantially conical shape of the wheel and extending along the shroud, each of the blades comprising: a leading edge closest to the air intake; a trailing edge farthest from the air intake, a cross section of the trailing edge taken along a reference plane having a substantially elliptical arc shape or a substantially arc shape, the reference plane contacting the trailing edge to be parallel to the outer peripheral surface; a tip edge connecting the leading edge and the trailing edge and opposing the shroud, the tip edge having a central curve extending along a center of a thickness of the tip edge from the leading edge to the trailing edge, the central curve having a tangential line touching a contact in the central curve, the tangential line having a tip edge inclination angle made by the rotation axis and the tangential line viewed in a reference direction which passes the contact and which is perpendicular to the rotation axis, the tip edge inclination angle increasing as the contact approaches a first maximum inclination point in the central curve, the first maximum inclination point being separated from both the leading edge and the trailing edge; a diffuser provided around the impeller to decelerate the fluid discharged from the trailing edge of the impeller in a centrifugal direction with respect to the rotation axis.
 5. The compressor according to claim 4, wherein each of the blades includes a lateral surface connecting the outer peripheral surface of the wheel and each of the leading edge, the training edge and the tip edge, and wherein each of the blades includes a corner rounded portion at a base of each of the blades adjacent to the trailing edge, the corner rounded portion having an arcuate cross section taken along an additional reference plane substantially perpendicular to the central curve to smoothly connect the lateral surface of the blade and the outer peripheral surface of the wheel, and wherein a thickness of each of the blades gradually decreases from the wheel towards the tip edge.
 6. The compressor according to claim 4, wherein each of the blades comprises a blade bottom opposite to the tip edge in a radial direction perpendicular to the rotation axis, the blade bottom being defined on the substantially conical shape of the wheel, the blade bottom having a bottom central curve extending along a center of a thickness of the blade bottom from the leading edge to the trailing edge, the bottom central curve having an additional tangential line touching a bottom contact in the bottom central curve, the additional tangential line having a hub surface side angle made by the rotation axis and the additional tangential line viewed in an additional reference direction which passes the bottom contact and which is perpendicular to the rotation axis such that the hub surface side angle increases as the bottom contact approaches a second maximum inclination point in the bottom central curve, the second maximum inclination point being separated from the both the leading edge and the trailing edge, wherein the tip edge inclination angle at the leading edge is smaller than the hub surface side angle at the leading edge, wherein the tip edge inclination angle at the trailing edge is substantially equivalent to the hub surface side angle at the trailing edge, and wherein the first maximum inclination point is nearer to the trailing edge than the second maximum inclination point. 